*{margin: 0;padding: 0;}
header{
    width: 100%;
    height: 90px;
    background-color: #fff;
    line-height: 50px;
    z-index: 1;
}
header div{
    width: 1200px;
    height: 90px;
    margin: 0 auto;
    position: relative;
    display: flex;
    justify-content: center;
}
header img{
    width: 200px;
    height: 23px;
    position: absolute;
    top:30px;
    left: 50px; 
    float: left;
    cursor: pointer;
}